The invention relates to a method for automatic starting of a diesel engine; when the ignition key is actuated, preheating and turning over of the engine by the starter are initiated and fuel injection is allowed only if the minimum temperature of the glow plugs required for starting the engine has been reached.
The invention also relates to a device for automatic starting of a diesel engine for application of a method such as that referred to above, with a control unit which may be activated by actuation of the ignition key, a device designed so that, when the ignition key is actuated, preheating and turnover of the engine by the starter are initiated and fuel injection is allowed only if the minimum temperature of the glow plugs required for starting the engine has been reached.
A method and device of the type referred to are disclosed in DE 38 35 214 C2. By means of the embodiments defined in this document automatic starting of a diesel engine is achieved in which the engine may be started without the need for waiting for completion of the preheat phase. Glow plugs of very high output and high-output batteries are required for generation of the high temperature in the shortest possible time.
The object of the invention is to reduce the time and/or energy required for the automatic starting.
Application of the method attains the object in that, when the ignition key is actuated, the throttle valve for delivery of air to the combustion chamber is also closed and is opened again at the earliest shortly before initiation of fuel injection.
With respect to the device the object is attained in that the control unit is designed so that, when the ignition key is actuated, the throttle valve for delivery of air to the combustion chamber also closes and is opened at the earliest shortly before initiation of fuel injection.
Application of the invention prevents cold air from striking the combustion chamber during preheating. As a result, the glow plug temperature required for starting of the engine is reached either more rapidly or with lower energy consumption. Hence this permits achievement of quicker starting of the engine, increase in the speed of starter rotation, and/or removal of the load on the battery in comparison to the conventional device. In addition, closing of the throttle valve causes less air to enter the engine, air which must be compressed needlessly during cranking of the engine in the first startup phase, that is before fuel injection.
The following developments of the method and the device serve the purpose of further optimization.
The method is preferably designed so that the beginning of the preheating and of starter initiation are separated in time so that the peak loads do not coincide chronologically. This prevents application of too great a peak load to the battery. Provision is suitably made such that actuation of the starter is delayed beyond beginning of the preheating so that the preheating peak load occurs before the starter peak load is applied. As a result, the very brief preheating period is lengthened somewhat.
Fuel injection occurs preferably at a point somewhat higher than the minimum temperature of the glow plugs, at a temperature optimal for ignition. The point in time selected for opening of the throttle valve, which is situated shortly before triggering of fuel injection, appropriately is such that optimal pressure and mixture relationships of air and fuel in the combustion chamber are achieved for ignition.
The device is correspondingly designed by configuring the control unit in such a way that or by providing it with a program such that the unit can cause the method steps in question to take place. It is also advisable for the control unit to be connected to a device for registering the temperature of the glow plugs. In this way reaching of the optimal temperature may be registered, even if the time at which such temperature is reached by the external temperature may be different under certain circumstances. The temperature may be registered directly with a temperature sensor. Since this is difficult, preference is given to indirect registration, for example, by way of the current consumption. The external temperature may also be registered and a waiting period may be determined as a function of it. In addition, the atmospheric pressure, which also exerts an influence, may be established and included in the method of determination of the waiting period. It is, of course, also possible to register other parameters and include them in control of the various elements of the device.
It is advisable to provide a quick-glow system for the preheating, one which because of its high output reaches the optimum temperature so quickly that the time required for starting the diesel engine no longer differs significantly from that needed for starting a gasoline-driven engine.